PEER-REVIEWED ARTICLE bioresources.com Saba et al. (2016). “Epoxy nanocomposites,” BioResources 11(3), 7721-7736. 7721 Fabrication of Epoxy Nanocomposites from Oil Palm Nano Filler: Mechanical and Morphological Properties Naheed Saba, a, * Paridah Md Tahir, a, * Khalina Abdan, b and Nor Azowa Ibrahim c The aim of this research was to fabricate epoxy nanocomposites by utilizing the developed nano filler from oil palm mills agricultural wastes oil palm empty fruit bunch (OPEFB) fibers for advanced applications. Epoxy-based polymer nanocomposites were prepared by dispersing 1, 3, and 5 wt. % nano OPEFB filler by using a high speed mechanical stirrer through hand lay-up technique. The mechanical (tensile and impact) properties and morphological properties of nano OPEFB/epoxy nanocomposites were examined and compared. Morphological properties were analyzed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) to look at the dispersion of the nano OPEFB filler in the epoxy matrix. The tensile and impact properties of nanocomposites increased until 3% nano filler loading, but beyond 3% they decreased. Overall mechanical properties reached maximum values for 3% loading, due to better stress transfer owing to homogenous dispersion of nano OPEFB filler within epoxy matrix. The observed results were also confirmed by SEM and TEM micrographs. Keywords: Epoxy; Oil Palm empty fruit bunch fiber; Nano filler; Nanocomposites; Mechanical properties; Morphological properties Contact information: a: Laboratory of Biocomposite Technology, Institute of Tropical Forestry and Forest Products(INTROP), University Putra Malaysia, 43400 Serdang, Selangor, Malaysia, Tel: +603-89468424; Fax: +603-89471896; b: Department of Biological and Agricultural Engineering, University Putra Malaysia, 43400 Serdang, Selangor, Malaysia; c: Department of Chemistry, Faculty of Science, University Putra Malaysia, 43400 Serdang, Selangor, Malaysia; * Corresponding authors: [email protected]; [email protected]INTRODUCTION Nanocomposites are the advanced engineered solid materials where at least one of the phases has a dimension in the nanometer range (1 nm to 100 nm), and are regarded as promising alternatives to overcome the drawbacks of polymer matrix, micro- and macro- conventional composites (Saba et al. 2014). Nanocomposites at lower filler contents can deliver superior mechanical/thermal properties, gas permeability, and flame retardancy compared with traditional materials (Saba et al. 2016b). The nanocomposites possess specific and remarkable properties that are critically required for different applications such as automotive, construction and buildings, food packaging, and electronics industries (Sun and Yao 2011; Saba et al. 2016c). Epoxy resins based on bisphenol A diglycidyl ether (DGEBA) are widely used in thermosetting engineered polymeric materials in the fields of electronic encapsulation, heavy equipment, dielectric materials, blending, composites, and nanocomposites (Mohan 2013; Saba et al. 2015b). Epoxy resins are leading the modern industries toward the development of high performance materials because of their thermal stability, mechanical properties, optically transparent properties, easy processing abilities, high stiffness, and
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PEER-REVIEWED ARTICLE bioresources.com
Saba et al. (2016). “Epoxy nanocomposites,” BioResources 11(3), 7721-7736. 7721
Fabrication of Epoxy Nanocomposites from Oil Palm Nano Filler: Mechanical and Morphological Properties
Naheed Saba,a,* Paridah Md Tahir,a,* Khalina Abdan,b and Nor Azowa Ibrahim c
The aim of this research was to fabricate epoxy nanocomposites by utilizing the developed nano filler from oil palm mills agricultural wastes oil palm empty fruit bunch (OPEFB) fibers for advanced applications. Epoxy-based polymer nanocomposites were prepared by dispersing 1, 3, and 5 wt. % nano OPEFB filler by using a high speed mechanical stirrer through hand lay-up technique. The mechanical (tensile and impact) properties and morphological properties of nano OPEFB/epoxy nanocomposites were examined and compared. Morphological properties were analyzed by transmission electron microscopy (TEM) and scanning electron microscopy (SEM) to look at the dispersion of the nano OPEFB filler in the epoxy matrix. The tensile and impact properties of nanocomposites increased until 3% nano filler loading, but beyond 3% they decreased. Overall mechanical properties reached maximum values for 3% loading, due to better stress transfer owing to homogenous dispersion of nano OPEFB filler within epoxy matrix. The observed results were also confirmed by SEM and TEM micrographs.
Saba et al. (2016). “Epoxy nanocomposites,” BioResources 11(3), 7721-7736. 7729
The reduction in mechanical (both tensile and impact) properties for 5% nano
OPEFB/epoxy nanocomposites with respect to 3% loading can be ascribed due to the poor
and inhomogeneous dispersion of nano OPEFB filler within the epoxy matrix.
.
Fig. 5. TEM micrograph for (a) 1%, (b) 3%, and (c) 5% nano OPEFB/ epoxy nanocomposites
Scanning Electron Microscopy (SEM) The primary goal of SEM is to determine the particle dispersion and to investigate
the variations or modifications occurred in the surface structure (morphology) of the
polymer matrix. The SEM studies in this research were made to analyze the surface
morphologies and interfacial adhesion between the incorporated nano OPEFB filler and
the epoxy matrix of the tensile fractured samples of nanocomposites. Figure 6 shows the
SEM of the tensile fractured samples of highly cross-linked epoxy composites.
The micrograph of epoxy composites (Fig. 6a) offered a smooth and glassy exterior
with numerous wavy or stream-like cracks. The cracks pattern of epoxy composite surface
clearly revealed its typical brittle plastic nature. Furthermore the direction of crack
propagation was from “upper left up” to “lower right” and in different planes. The wavy
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Saba et al. (2016). “Epoxy nanocomposites,” BioResources 11(3), 7721-7736. 7730
and brittle nature indicates that resistance towards cracking or rupturing and its propagation
was considerably lesser in epoxy composites. Thus relatively less energy required during
tensile fracturing of epoxy composites. A similar SEM micrograph image for epoxy
composites was also reported by other researchers (Dadfar and Ghadami 2013; Quan and
Ivankovic 2015).
Fig. 6. SEM micrographs of tensile fractured images of epoxy composites. (a) 1000x and (b) 3000x magnification
The SEM micrographs of 1%, 3%, and 5% nano OPEFB/epoxy nanocomposites
are shown in Figs. 7 to 9. From the figures it is evident that the SEM morphology of 1%,
3%, and 5% nano OPEFB/epoxy nanocomposites was quite similar, but are relatively
different than epoxy composites. The irregular and jagged fracture surface of all nano
OPEFB/epoxy nanocomposites displayed relatively less brittle and ductile failure nature of
the epoxy matrix (Lee et al. 2010; Yang et al. 2011). The incorporation of nano OPEFB
filler in the brittle, soft and smooth epoxy material reduces the number of crack lines and
made the surface coarser, thus leading to matrix deformation and finally to the deflection
of cracks. Consequently, fluctuations in the crack propagation pathway from straight,
conventional and unruffled growth were observed in the epoxy nanocomposites.
Comparative results were also reported in the literature, where incorporation of nano oil
palm ash particles in the epoxy matrix displayed similar SEM images (Abdul Khalil et al.
2010). Figure 7 shows the tensile fractured surface of 1% nano OPEFB/epoxy
nanocomposites having the crack propagation from up to down. Tensile fractured surface
of 1% nano OPEFB/epoxy nanocomposites shows a slightly rougher and jagged texture
compare to tensile fracture surfaces of epoxy composites, with no particle clumping.
Figure 8 shows the SEM micrographs of tensile fractured surface of 3% nano
OPEFB/epoxy nanocomposites. The SEM images clearly displayed the rapid crack
proliferation, indicating that cracks followed more twisting paths in well dispersed 3%
nano OPEFB/epoxy nanocomposites. This made the surface coarser and rougher as no
transverse river line or wavy marking was observed. Noticeably, 1% and 3% nano OPEFB
filler loading displayed cloudy and irregular tensile fractured surfaces with no obvious
agglomeration within the epoxy matrix. This indicates that relatively higher amounts of
energy were consumed to break the 3% nano OPEFB/epoxy nanocomposites sample as the
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Saba et al. (2016). “Epoxy nanocomposites,” BioResources 11(3), 7721-7736. 7731
dispersed nano filler particles hindered the crack propagation path. Consequently the
increase in tensile and impact properties of 3% nano OPEFB/epoxy nanocomposites also
correspond to crack deflections process. This statement are also in agreement with other
research findings (Liu et al. 2011). The 3% nano OPEFB/epoxy nanocomposites displayed
better resistance toward crack propagation due to the deflection of cracks under tensile
stress conditions.
Fig. 7. SEM micrographs of the tensile fracture texture of 1% nano OPEFB filler loading. (a) 1000x and (b) 3000x magnification
Fig. 8. SEM micrographs of tensile fractured sample of 3% nano OPEFB filler loading. (a) 1000x and (b) 3000x magnification
The 5% nano OPEFB/epoxy nanocomposites displayed higher roughness in certain
spaces, but had no wavy or river line marking of the kind seen in the 3% nano
OPEFB/epoxy nanocomposites (Fig. 9). The presence of agglomerations leads to a
reduction in effective interaction volume as well as large continuous interfacial zones in
added nano OPEFB filler of 5% nano OPEFB/epoxy nanocomposites are clearly visible in
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Saba et al. (2016). “Epoxy nanocomposites,” BioResources 11(3), 7721-7736. 7732
Fig. 9a. Presence of agglomeration, created blank spaces or voids (Fig. 9b) within the
polymer matrix, reflecting poor particle dispersion. After the initial tensile impact, the
crack propagated in the direction of the tension, proceeding to the weak interfaces, where
there were comparatively lesser nano filler ultimately leading to the failure or damage to
the composites material. The presence of dispersed nano OPEFB filler particles acted as
obstacles to premature cracks or ruptures, but there were still many places where there are
no particles present in order to resist the crack propagation, as displayed in (Fig. 9c). The
presence of voids and agglomerated structures of the nano OPEFB filler particles within
epoxy matrix act as stress concentration sites to initiate cracking by the applied stress. The
cracks penetrate the material, while the aggregates act as weak points that initiate the
preliminary rupture or failure of the nanocomposites on exposure to mechanical testing
(Montazeri and Chitsazzadeh 2014). Thus, the 5% nano OPEFB/epoxy nanocomposites
had reduced mechanical properties, especially tensile strength, compared to 3% nano
OPEFB/epoxy nanocomposites.
Fig. 9. SEM micrographs of the tensile fracture texture showing (a) agglomerations, (b) void, and (c) deep fracture in 5% nano OPEFB filler loading. (a) 3000x (b) 3000x and (c) 1000x magnification
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Saba et al. (2016). “Epoxy nanocomposites,” BioResources 11(3), 7721-7736. 7733
CONCLUSIONS 1. The 3% nano OPEFB/epoxy nanocomposites displayed better tensile and impact
properties relative to the other epoxy nanocomposites and neat epoxy in this study.
Considerably higher Brownian motion of the dispersed nano OPEFB filler within epoxy
matrix and better interfacial interaction between 3% nano OPEFB filler and epoxy matrix
results in an efficient stress transfer in 3% nano OPEFB/epoxy nanocomposites with
respect to the 1% and 5% nanocomposites.
2. TEM analysis confirmed that 3% nano OPEFB filler loading resulted in good/uniform
distribution and dispersion of particles with no evidence of agglomerations and voids
content in the space. In contrast to 3% filler loading, the 5% displayed poor dispersion of
the nano filler in the epoxy matrix.
3. SEM results were in agreement with the TEM and mechanical properties results.
4. Overall, the incorporation of 3% nano OPEFB filler loading into the epoxy matrix
showed optimum, reasonable, and better mechanical properties.
ACKNOWLEDGMENTS The authors are thankful to the Universiti Putra Malaysia, Malaysia for supporting this
research through Putra Grant No. 9420700.
REFERENCES CITED Abdellaoui, H., Bensalah, H., Echaabi, J., Bouhfid, R., and Qaiss, A. (2015).
“Fabrication, characterization and modelling of laminated composites based on